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Introduces a configure method pattern for Supplier-style configuration and a common SingletonSupplier decorator for method reference suppliers. Also declares jcache.config and jcache.interceptor for non-null conventions. Issue: SPR-17021pull/1887/merge
Juergen Hoeller
8 years ago
53 changed files with 766 additions and 311 deletions
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/* |
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* Copyright 2002-2018 the original author or authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package org.springframework.util.function; |
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import java.util.function.Supplier; |
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import org.springframework.lang.Nullable; |
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import org.springframework.util.Assert; |
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/** |
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* A {@link java.util.function Supplier} decorator that caches a singleton result and |
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* makes it available from {@link #get()} (nullable) and {@link #obtain()} (null-safe). |
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* |
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* <p>A {@code SingletonSupplier} can be constructed via {@code of} factory methods |
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* or via constructors that provide a default supplier as a fallback. This is |
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* particularly useful for method reference suppliers, falling back to a default |
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* supplier for a method that returned {@code null} and caching the result. |
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* |
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* @author Juergen Hoeller |
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* @since 5.1 |
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* @param <T> the type of results supplied by this supplier |
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*/ |
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public class SingletonSupplier<T> implements Supplier<T> { |
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@Nullable |
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private final Supplier<? extends T> instanceSupplier; |
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@Nullable |
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private final Supplier<? extends T> defaultSupplier; |
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@Nullable |
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private volatile T singletonInstance; |
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/** |
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* Build a {@code SingletonSupplier} with the given singleton instance |
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* and a default supplier for the case when the instance is {@code null}. |
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* @param instance the singleton instance (potentially {@code null}) |
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* @param defaultSupplier the default supplier as a fallback |
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*/ |
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public SingletonSupplier(@Nullable T instance, Supplier<? extends T> defaultSupplier) { |
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this.instanceSupplier = null; |
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this.defaultSupplier = defaultSupplier; |
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this.singletonInstance = instance; |
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} |
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/** |
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* Build a {@code SingletonSupplier} with the given instance supplier |
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* and a default supplier for the case when the instance is {@code null}. |
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* @param instanceSupplier the immediate instance supplier |
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* @param defaultSupplier the default supplier as a fallback |
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*/ |
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public SingletonSupplier(@Nullable Supplier<? extends T> instanceSupplier, Supplier<? extends T> defaultSupplier) { |
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this.instanceSupplier = instanceSupplier; |
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this.defaultSupplier = defaultSupplier; |
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} |
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private SingletonSupplier(Supplier<? extends T> supplier) { |
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this.instanceSupplier = supplier; |
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this.defaultSupplier = null; |
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} |
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private SingletonSupplier(T singletonInstance) { |
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this.instanceSupplier = null; |
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this.defaultSupplier = null; |
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this.singletonInstance = singletonInstance; |
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} |
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/** |
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* Get the shared singleton instance for this supplier. |
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* @return the singleton instance (or {@code null} if none) |
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*/ |
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@Override |
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@Nullable |
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public T get() { |
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T instance = this.singletonInstance; |
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if (instance == null) { |
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synchronized (this) { |
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instance = this.singletonInstance; |
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if (instance == null) { |
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if (this.instanceSupplier != null) { |
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instance = this.instanceSupplier.get(); |
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} |
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if (instance == null && this.defaultSupplier != null) { |
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instance = this.defaultSupplier.get(); |
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} |
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this.singletonInstance = instance; |
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} |
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} |
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} |
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return instance; |
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} |
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/** |
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* Obtain the shared singleton instance for this supplier. |
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* @return the singleton instance (never {@code null}) |
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* @throws IllegalStateException in case of no instance |
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*/ |
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public T obtain() { |
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T instance = get(); |
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Assert.state(instance != null, "No instance from Supplier"); |
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return instance; |
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} |
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/** |
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* Build a {@code SingletonSupplier} with the given singleton instance. |
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* @param instance the singleton instance (never {@code null}) |
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* @return the singleton supplier (never {@code null}) |
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*/ |
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public static <T> SingletonSupplier<T> of(T instance) { |
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return new SingletonSupplier<>(instance); |
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} |
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/** |
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* Build a {@code SingletonSupplier} with the given singleton instance. |
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* @param instance the singleton instance (potentially {@code null}) |
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* @return the singleton supplier, or {@code null} if the instance was {@code null} |
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*/ |
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@Nullable |
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public static <T> SingletonSupplier<T> ofNullable(@Nullable T instance) { |
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return (instance != null ? new SingletonSupplier<>(instance) : null); |
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} |
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/** |
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* Build a {@code SingletonSupplier} with the given supplier. |
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* @param supplier the instance supplier (never {@code null}) |
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* @return the singleton supplier (never {@code null}) |
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*/ |
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public static <T> SingletonSupplier<T> of(Supplier<T> supplier) { |
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return new SingletonSupplier<>(supplier); |
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} |
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/** |
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* Build a {@code SingletonSupplier} with the given supplier. |
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* @param supplier the instance supplier (potentially {@code null}) |
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* @return the singleton supplier, or {@code null} if the instance supplier was {@code null} |
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*/ |
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@Nullable |
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public static <T> SingletonSupplier<T> ofNullable(@Nullable Supplier<T> supplier) { |
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return (supplier != null ? new SingletonSupplier<>(supplier) : null); |
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} |
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} |
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@ -0,0 +1,43 @@
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/* |
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* Copyright 2002-2018 the original author or authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package org.springframework.util.function; |
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import java.util.function.Supplier; |
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import org.springframework.lang.Nullable; |
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/** |
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* Convenience utilities for {@link java.util.function.Supplier} handling. |
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* |
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* @author Juergen Hoeller |
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* @since 5.1 |
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* @see SingletonSupplier |
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*/ |
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public abstract class SupplierUtils { |
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/** |
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* Resolve the given {@code Supplier}, getting its result or immediately |
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* returning {@code null} if the supplier itself was {@code null}. |
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* @param supplier the supplier to resolve |
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* @return the supplier's result, or {@code null} if none |
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*/ |
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@Nullable |
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public static <T> T resolve(@Nullable Supplier<T> supplier) { |
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return (supplier != null ? supplier.get() : null); |
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} |
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} |
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@ -0,0 +1,9 @@
@@ -0,0 +1,9 @@
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/** |
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* Useful generic {@code java.util.function} helper classes. |
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*/ |
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@NonNullApi |
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@NonNullFields |
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package org.springframework.util.function; |
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import org.springframework.lang.NonNullApi; |
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import org.springframework.lang.NonNullFields; |
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